1. Field of the Invention
The present invention relates to a gas sensor, and in particular relates to an oxygen sensor.
2. Description of the Related Art
FIG. 1 shows a conventional oxygen sensor 10 comprising a first electrode 11, a second electrode 12, a chamber 13, an ion conductive layer 14 and a gas selective layer 15. The chamber 13 is formed in a center of the ion conductive layer 14. A first electrode 11 is formed on an inner wall of the chamber 13. The second electrode 12 is formed on an outer wall of the ion conductive layer 14. The gas selective layer 15 is coated on the second electrode 12. In gas detection, the chamber 13 is connected to an environmental gas, the environment gas reacts with the first electrode 11, and a gas to be measured passes the gas selective layer 15 to react with the second electrode 12. The oxygen consistency of the environmental gas differs from that of the gas to be measured. Thus, a voltage difference is formed between the first electrode 11 and the second electrode 12. The voltage difference generates an electromotive force to conduct the first electrode 11 and the second electrode 12 through the ion conductive layer 14. The oxygen consistency of the gas to be measured is obtained by measuring the voltage difference.
Conventionally, the ion conductive layer 14 is made by an injection, a dry press or an extrusion process. A conventional ion conductive layer 14 is thick with minimal sensitivity and high costs.